BACKGROUND

T(H)17 cells are of pathologic relevance in autoimmune disorders and presumably also in allergy and asthma. Regulatory T (Treg) cells, in contrast, suppress inflammatory and allergen-driven responses. Despite these disparate functions, both T-cell subsets have been shown to be dependent on TGF-beta for their development.

OBJECTIVE

The aim of the study was to analyze the differentiation and function of human T(H)17 cells in comparison with other T(H) cell subsets.

METHODS

Naive human CD4(+) T cells were differentiated in vitro, and gene expression was analyzed by means of quantitative real-time PCR, ELISA, and immunofluorescence. The function of T(H) cell subsets was assessed by monitoring the response of primary bronchial epithelial cells in coculture experiments.

RESULTS

In vitro differentiated T(H)17 cells differ from Treg and other T(H) cells in their potency to induce IL-6 and IL-1beta expression in primary bronchial epithelial cells. TGF-beta, IL-1beta, IL-6, and IL-23 are necessary during T(H)17 cell differentiation to acquire these functions, including IL-17 production. In contrast, TGF-beta alone is necessary and sufficient to induce the transcription factor RORC2. This transcription factor, previously thought to be specific for T(H)17 cells, is also expressed in Treg cells, CD25(+) cells, cytotoxic T cells, and natural killer T cells.

CONCLUSION

This study demonstrates mechanisms of differentiation to human T(H)17 cells, a subset that effectively and uniquely modulates the function of primary bronchial epithelial cells.